In general, a DC/DC converter is an electronic circuit that accepts a DC input (i.e., a power signal) at one voltage level and converts it to a DC output at a lower or higher voltage level. Such a converter is well-suited for circuit boards containing operating circuitry which requires a DC signal having a particular voltage level but that only has access to a different DC signal having a different voltage level. For example, one conventional processor requires both a 3.3 Volt DC signal and a 2.5 Volt DC signal for proper operation. If a processor circuit board manufacturer only has access to a 12 Volt DC signal, the manufacturer can manufacture a processor circuit board having the conventional processor and a set of converters which provides the 3.3 and 2.5 Volt DC signals to the processor in response to the 12 Volt DC signal thus enabling the processor to operate properly.
Some processors require multiple voltages in a particular startup sequence. For example, the above-described conventional processor requires a soft start 3.3 Volt DC signal and a soft start 2.5 Volt DC signal. In accordance with the startup sequence, the 3.3 Volt DC signal and the 2.5 Volt DC signal may never vary from each other by more than 1.2 Volts, and the 2.5 Volt DC signal may never exceed the 3.3 Volt DC signal by more than 0.4 Volts. For such a processor, the circuit board manufacturer typically custom designs external control logic and installs the external control logic between the outputs of the converters (i.e., metal contacts) and the processor. The control logic typically resides on a section of circuit board space that is approximately 2 inches by 2 inches between the converters and the processor, and is configured to electrically isolate the processor from the converter outputs in the event the converters improperly provide the power signals. Accordingly, if the converters provide the power signals out of the particular startup sequence (e.g., if the 3.3 Volt DC signal varies from the 2.5 Volt DC signal by more than 1.2 Volts), the control logic disconnects the processor from the converter outputs to avoid damaging the processor.
Some converters have other special features. For example, one conventional converter includes (i) a sensing contact and (ii) a feedback circuit connected to the sensing contact. A circuit board manufacturer typically connects one end of an external Schottky diode to the converter output, and the other end of the external Schottky diode to the sensing contact. If the output voltage sensed at the sensing contact (i.e., sensed across the Schottky diode) is too high, the feedback circuit directs the converter to provide less current to lower the output voltage. If the output voltage is too low, the feedback circuit directs the converter to provide more current to increase the output voltage.
In some high current demand situations, circuit board manufacturers may install multiple converters that provide the same output voltage. For example, a particular converter may not be able to provide enough current to meet the demands of a particular processor. In such a situation, the manufacturer can install two converters having the above-described feedback capabilities onto a processor circuit board to accommodate the high current demands of the processor. The two converters provide the same output voltage and enough current to satisfy the high current needs of the processor. During periods of operation that require less current, the feedback circuits of the two converters will sense an increase in the output voltage provided by the converters and direct the converters to provide less current.
As another example of a converter with a special feature, some converters include overvoltage protection circuits. One conventional converter includes (i) a switched-capacitor circuit that provides an output voltage, (ii) a converter output (e.g., a metallic contact) for connecting to external operating circuitry (e.g., a processor), and (iii) an overvoltage protection circuit interconnected between the switched-capacitor circuit and the converter output. The overvoltage protection circuit is configured to disconnect the switched-capacitor circuit from the converter output if the output voltage exceeds a predetermined threshold. Accordingly, when the output voltage of the power signal is excessive, the overvoltage protection circuit prevents the power signal from reaching and possibly damaging the external operating circuitry.
As yet another example, some converters include trim pins which, when soldered to a resistor or a voltage divider that provides a particular voltage, causes the converter to provide an output voltage that is based on the particular voltage. For example, suppose that a circuit board manufacturer (i) requires a 3.0 Volt DC signal and (ii) has both expensive 3.0 Volt converters and less expensive 3.3 Volt converters available. The manufacturer may be able to use the less expensive 3.3 Volt converters by utilizing the trim pin feature of the 3.3 Volt converters. To this end, the manufacturer can solder the trim pin of each 3.3 Volt converter to a resistor providing an appropriate voltage that directs the 3.3 Volt converter to provide the 3.0 Volt DC signal rather than a 3.3 Volt DC signal thus enabling the manufacturer to take advantage of the lower cost 3.3 Volt converters.